I neglected my wife for years, didn't give her love the way she needed and the way I should have. Sometimes when things seem really bleak, I feel like I blew it, my one chance.
The feeling goes away. When it comes, I try and focus on something good in my life, something I'm thankful for, something I DID get right.
It'll get better. Dwell on the good in your life, even if it's a small thing.